Geography of Antarctica
Introduction to Geography of AntarcticaAntarctica is the continent that covers and surrounds the South Pole.
Antarctica, the ice-locked landmass around the South Pole. The name means "opposite the Bear" (the northern constellation), or "opposite the Arctic." It is the most remote and desolate of all the continents. Serious exploration of Antarctica did not begin until the end of the 19th century. Today this vast inhospitable area of bitter winds and cold is the temporary home of thousands of scientists from many countries.
Including its permanent ice, Antarctica has an area of about 5,500,000 square miles (14,250,000 km2). Almost all of this roughly circular continent is covered by an immense polar ice cap, larger than the United States, Mexico, and Central America combined. Antarctica's greatest extent is about 3,500 miles (5,630 km), from the northern tip of the Antarctic Peninsula to the coast of Wilkes Land. The distance from the front of the Ross Ice Shelf across to the Princess Astrid Coast is 2,200 miles (3,540 km).
Surrounding Antarctica are the Pacific, Atlantic, and Indian oceans, whose southernmost waters are sometimes called the Antarctic Ocean. The coast is deeply indented by the Ross Sea, which opens onto the Pacific, and by the Weddell Sea, which opens onto the Atlantic.
In Antarctica is the South Pole, the earth's southernmost point. It lies far inland at an elevation of 9,200 feet (2,800 m) and is the site of the Amundsen-Scott Station, a United States scientific base. Off the coast of Wilkes Land, nearly 1,700 miles (2,740 km) from the South Pole, is the south magnetic pole. Also in Antarctica, near Russia's Vostok base about halfway between these two poles, is the south geomagnetic pole.
The Antarctic sky is sometimes lighted by magnificent displays of the Aurora Australis, or Southern Lights.
The continent consists of two great regions, East Antarctica and West Antarctica. East Antarctica, the larger of the two, lies mainly between the Transantarctic Mountains and the Indian Ocean. It is more than three times the size of West Antarctica and consists of an ice-capped block of geologically old, stable rock, largely above sea level. In contrast, West Antarctica, with much of its land below sea level, is an ice-covered archipelago of geologically more recent origin. Many of the mountain peaks visible above the ice cap were volcanically formed; some are active volcanoes. Probably best known is Mount Erebus, which towers high above McMurdo Station, a United States scientific base on Ross Island.
The Antarctic ice cap covers some 98 per cent of the continent's surface. It rises as an immense, somewhat flattened dome to more than 13,000 feet (3,960 m) above sea level in the interior. No other continent has as high an average elevation as Antarctica. The ice cap averages 7,000 to 8,000 feet (2,130 to 2,440 m) in thickness; its greatest known thickness is 15,670 feet (4,776 m). Across much of the continent high winds have packed the snow into parallel ridges called sastrugi, which form a major obstacle to aircraft landings and surface transportation. In some places the surface of the ice cap is fractured by wide cracks, or crevasses, often hidden by thin "bridges" of snow.
The Transantarctic Mountains extend across the continent in an S-curve from the Theron Mountains of Coats Land through the Queen Maud Mountains to Cape Adare in Victoria Land---a distance of about 2,300 miles (3,700 km). Their highest peaks and ridges rise above the polar ice, reaching heights of more than 14,000 feet (4,270 m) above sea level. The continent's highest known point is in the Ellsworth Mountains, in Ellsworth Land, where the bare top of Vinson Massif lies 16,864 feet (5,140 m) above sea level. There are also lofty mountain ranges near the coasts of Marie Byrd Land and Queen Maud Land, in the American Highland, and on the Antarctic Peninsula. Jutting through the ice in numerous areas are isolated bare peaks called nunataks.
Nearly all of Antarctica's coast is buried by the polar ice cap. In several areas the ice pushes out into the ocean to form enormous floating sheets called ice shelves. The largest are the Ross Ice Shelf, the Ronne Ice Shelf, the Larsen Ice Shelf, and the Filchner Ice Shelf.
Some ice shelves are fed, in part, by huge glaciers moving down mountain valleys to the coasts. There are also glaciers that flow directly into the sea as long floating tongues, known as glacier tongues or iceberg tongues.
Many billion tons of ice break off from the cliff-like outer edges of the ice shelves each summer and, characteristically in the form of flat-topped icebergs, drift northward. Other masses of ice, called sea ice, originate from the freezing of seawater and extend great distances offshore, especially during winter. The breakup of the sea ice during summer gives rise to freely floating ice known as pack ice.
No place on earth has a climate as cold as Antarctica's. Average daily temperatures nearly everywhere are below freezing even during the warmest months (November to February), when the sun shines continuously on most of Antarctica. Winter temperatures are lowest on the polar plateau, where they average as low as -90° F. (-68° C.). A temperature of -128.6° F. (-89.2° C.), the world's record, was recorded in 1983 at the Soviet Union's Vostok base, about 800 miles (1,290 km) from the South Pole. Winter readings along the coast in some places average from -30° F. to -5° F. (-34° C. to - 21° C.). The warmest part of Antarctica is the northernmost fringes of the Antarctic Peninsula, where average summer temperatures are above freezing from one to four months of the year.
Snowfall is greatest near the relatively warm ocean, where yearly accumulations average the equivalent of 8 to 30 inches (200 to 760 mm) of rain, depending on location. Little snow falls in the dry interior. The average annual snowfall for the continent as a whole is equivalent to roughly 4 inches (100 mm) of rain.
Antarctic snow is very dry and powdery. It is whipped by fierce winds into blizzards longer and more intense than anywhere else in the world. These winds, sharpening the already bitter cold of the Antarctic, sometimes sweep down the slopes of the polar plateau at speeds up to 200 miles per hour (320 km/h), especially along the Adélie Coast. Windless days are rare.
Occasionally, low cloud layers cause a uniform white light to bounce back and forth between the clouds and the snow. In this eerie condition, known as whiteout, the horizon and all shadows vanish and a person can lose all sense of direction.
Land and Ocean Life
Because of its severely harsh climate and natural environment, Antarctica is largely a lifeless continent. Plants are limited primarily to relatively small ice-free coastal areas during summer and consist mostly of mosses and liverworts. A few species of flowering plants, including several grasses, are found on the Antarctic Peninsula. Lichens grow on rocks and firm soil. There are no trees or shrubs. Most of the land animals are tiny arthropods, including mites, lice, springtails, and a wingless fly. All are dormant for most of the year.
In sharp contrast to the land, the sea supports abundant life. Waters in the southern oceans are rich in nutrients and teem with plankton and krill, small shrimp-like crustaceans. Krill are perhaps the largest single source of natural protein in the world and are potentially of great commercial value.
Vertebrate animals that either live in or frequent the Antarctic region include whales, seals, and penguins and other sea-birds. Whales are generally more abundant in Antarctic waters than in other oceans. Most numerous are sperm, minke, fin, sei, blue, and humpback whales. Killer whales also roam the ocean. Among the seals found in the icy waters are crabeater, elephant, leopard, Ross, and Weddell seals.
The birds of Antarctica obtain their food from the sea. The penguin is the animal probably most symbolic of the continent. Adélie and emperor penguins live and breed in vast colonies along Antarctica's shores.
Petrels, albatrosses, skuas, gulls, terns, and other seabirds visit Antarctica during the brief summer. Some of the birds nest on the continent's rocky islands and shores, especially along the Antarctic Peninsula.
For centuries, it was believed that a great unknown continent encompassed much of the southern end of the globe. Attempting to locate this land in 1772-75, James Cook, a British explorer, became the first to cross the Antarctic Circle and to sail around the continent (although not sighting it). His voyage neither proved nor disproved the continent's existence, but did indicate that if there were any such land its size had been greatly exaggerated.
During 1819-21, a similar circumnavigation of Antarctica was made by Fabian von Bellingshausen, a Russian captain. He discovered and named Peter I and Alexander I islands, within the Antarctic Circle.
While searching for seal breeding grounds in 1820, Nathaniel Palmer of the United States sighted the peninsula later called Palmer Peninsula. (It was renamed Antarctic Peninsula in 1964.) This may have been the first actual sighting of the mainland, although there have been conflicting claims. In 1823 a British sealer, James Weddell, sailed into the sea later named for him. Charles Wilkes, commanding a U.S. Navy expedition, discovered Wilkes Land in 1840 and was the first to recognize the existence of Antarctica as a continent.
Up to that time, no one had attempted to land because of the surrounding pack ice. In 1842, however, James C. Ross, commander of the British ships Erebus and Terror, steered through the ice. A massive floating ice shelf more than 100 feet (30 m) high, later called the Ross Ice Shelf, halted his southward progress. Ross sailed eastward along the Antarctic coast, sighting and naming Cape Adare, Victoria Land, Possession Island, and Mount Erebus.
About mid-century, the attention of most explorers turned to the Arctic. Interest in Antarctica did not revive until the 1880's, although whalers and sealers continued to search its waters.
One of the first important landings on Antarctica was made by Leonard Kristensen, a Norwegian whaler, in 1895. A Belgian scientific expedition under Adrian de Gerlache was the first to winter within the Antarctic Circle, 1898-99, when its ship was trapped in the ice. A year later, a British party led by the Norwegian explorer C. E. Borchgrevink wintered on the continent.
These early explorers surveyed only small coastal areas. Exploration of the interior did not begin until after 1900. During 1901-04, the expedition of Robert F. Scott discovered King Edward VII Land and made several sledge journeys, one reaching a point some 500 miles (800 km) from the South Pole. In 1909 Ernest Shackleton led a British party to within 97 miles (156 km) of the Pole.
The South Pole was reached on December 14, 1911, by the Norwegian Roald Amundsen and four companions, who made the trip from the Bay of Whales by dog sledge in 57 days. About a month later a British expedition led by Scott reached the Pole on foot by a different route. The five-man Scott party perished on the return journey.
After the end of World War I, expeditions were more numerous and increasingly better equipped. Greater emphasis was given to gathering scientific data. The airplane was first employed in Antarctic exploration by Sir Hubert Wilkins, an Australian, who flew most of the length of Palmer Peninsula in 1928.
Also in 1928, Richard E. Byrd of the United States began the construction of the Little America base in the Bay of Whales. He made the first plane flight over the Pole on November 29, 1929, covering the 1,600-mile (2,575-km) round trip in 19 hours; the plane was piloted by Bernt Balchen. Byrd conducted several expeditions for the U.S. Navy, setting up a number of bases and amassing important meteorological and geographic information.
During 1929-30, Sir Douglas Mawson of Australia discovered Mawson Coast, the coast of MacRobertson Land. In the 1930's, Lincoln Ellsworth led two American expeditions and made the first aerial crossing of Antarctica.
In the mid-1940's, scientific interest in Antarctica and its surrounding lands greatly increased. A number of nations planned to establish research stations in the area. During 1946-47, the United States conducted the massive Operation Highjump, which included some 4,000 men and more than 30 ships and planes. Rear Admiral George Dufek of the U.S. Navy made the first airplane landing near the Pole, in 1956. Shortly after, the United States' Amundsen-Scott station was set up there. The first overland crossing of the continent was completed by a British Commonwealth party under Vivian Fuchs, 1957-58, aided by a New Zealand party led by Sir Edmund Hillary. In 1966 an American expedition was the first to climb Vinson Massif, the highest peak in the Antarctic.
Seven nations have made formal territorial claims in Antarctica—Argentina, Australia, Chile, France, Great Britain, New Zealand, and Norway. Some of the claims overlap; about 15 per cent of the continent is unclaimed. The United States, Russia, and a number of other countries neither recognize these territorial claims nor make claims of their own.
Under the terms of the Antarctic Treaty of 1959, all territorial claims are being held in abeyance. The treaty was originally adopted by Argentina, Australia, Belgium, Chile, France, Great Britain, Japan, New Zealand, Norway, South Africa, the Soviet Union, and the United States, and several other nations later became treaty members. The world's nations as a whole, however, have yet to agree upon the legal status of the continent.
Since Antarctica is virtually untouched by civilization and has little animal and plant life, it serves as an ideal natural laboratory for the geophysical sciences. During the International Geophysical Year, 1957-58, 12 nations cooperated in beginning a thorough investigation of the south polar region. This undertaking contributed to the creation of the Antarctic Treaty of 1959; in addition to postponing territorial claims, the 12 signatory nations agreed to use the region jointly for peaceful and scientific purposes only. Other nations have subsequently joined in the research work. In 1988 the treaty nations signed an agreement that would govern development of all natural resources in Antarctica.
Exploratory studies of Antarctica's surface are now largely complete, and investigations have turned to the natural processes at work in the atmosphere, the ice, and the sea.
Extensive geological studies provide a general outline of the region's geology and support the theory of plate tectonics. (See Geology, subtitle Physical Geology: Plate Tectonics.) Investigations indicate Antarctica was once part of ancient Gondwanaland, a giant landmass that began breaking up and drifting apart some 125,000,000 years ago. Eventually, Australia, South America, Africa, the Indian subcontinent, and Antarctica were formed. Of special geological interest are the potential mineral and petroleum resources of the continent and the adjoining seabed. Fossils and exposed rock formations and coal seams provide clues to the continent's geological past. At one time there was no ice in Antarctica, and trees and large animals flourished.
Much of the glacial research in Antarctica has centered on the extent of the ice sheet and its surface characteristics, such as temperature and snow accumulations. Under increasing study, using such techniques as radio-echo sounding and ice-coring, is the internal nature of the ice. Scientists have also been trying to determine the age of the ice; the ice of East Antarctica is believed to be as much as 25,000,000 years old, while that of West Antarctica is much younger.
Using ground instruments, weather balloons, and satellites, meteorologists make detailed observations of the air of Antarctica. They measure humidity, temperature, air pressure, wind speed and direction, precipitation, radiation, and the ozone and carbon dioxide content of the atmosphere. With this information they attempt to determine the effect of Antarctic weather on the weather elsewhere. Observations in the late 1980's revealed widespread seasonal reductions in the ozone concentrations over Antarctica. (See Ozone.)
Because Antarctic waters circle the globe without being interrupted by a landmass, they are ideal for studying waves and the chemical and physical properties of seawater. They also provide information on ocean currents and the temperature variations of the world's oceans.
The presence of the south geomagnetic pole and the relative absence of radio-frequency noise (due to a scarcity of thunderstorms) make Antarctica particularly suitable for studying auroras, the ionosphere, cosmic radiation, the sun, the earth's magnetic field, and many other phenomena.